Synching Files & Folders via iCloud from an Exterior Hard Drive

So... I think from looking around, what I want to do is not possible with iCloud, without laborious workarounds. But I'll put the question out there.

I have a newer iMac, meaning since they started reducing storage capacities in lieu of cloud storage. I opted for an exterior hard drive to store most of my files. I have added my "Desktop & Documents" to iCloud. So I can access the limited files and folders I'm able to store on my iMac, but when it comes to the files and folders on my hard drive, which is the bulk of my stuff, other than dragging individual files and folders over to the iCloud Drive, so that I can access them remotely, I'm not sure how I can achieve remote access to my exterior drive or if that's even possible.

The problem with moving files and folders from my desktop to my iCloud Drive, is that they are not actually "synched," in the truest sense of the word. They are moved as they are in that moment to iCloud for storage, but when edits are made in individual documents in their original location on my iMac, they do not automatically update in iCloud.

So... for example, if I edit a client's file, and forget to replace the file or folder it's in to iCloud, I may show up to a remote meeting with the unedited version accessed remotely through iCloud.

I think that what I want is not possible. And I've tried SugarSynch (which does allow this) and other similar products, which as others have said, do not work well on a Mac.

Thanks in advance.